1. Technical Field
This invention relates, generally, to downhole well tools and methods used in drilling and servicing of hydrocarbon wells, such as oil and gas wells. More specifically, this invention relates to tools used to clean wellbores and to clean the fluids contained in the wellbores.
2. Background Art
The invention provides a well cleanout tool, specifically, this invention relates to tools having external cleaning elements, such as a wiper, assembled in a tubing string. These tools are used to clean wellbores and to clean the fluids contained in the wellbores by circulating fluids through and around the tubing string. One, cleaning method includes running the tool into the well while cleaning the wellbore and forcing down the annulus and up through the tubing string. Another method includes cleaning through forward and reverse circulation. The tool of the present invention accommodates and can be used to perform all three methods.
As used herein, the words “comprise,” “have,” “include,” and all grammatical variations thereof are each intended to have an open, non-limiting meaning that does not exclude additional elements or steps. The term “wellbore” refers to the subterranean well opening, including cased and uncased. The term “tubing string” is used generically to refer to tubular members positioned in a wellbore, such as drill pipe, tubing and the like. The terms “forward circulation” and “reverse circulation” are used to describe well known well processes. “Forward circulation” refers to processes wherein well fluids are pumped into the wellbore through the interior of the tubing string and flow out of the well around the outside of the tubing string (annulus). In “reverse circulation”, well fluids are pumped into the well along the outside of the string and are discharged from the well through the interior of the string. The term “well fluids” refers broadly to any fluids found in a wellbore. The term “wiper” is used broadly herein to refer to a swab cup-like structure that extends to the wellbore wall. The wiper forms a sliding seal with the interior wall of the wellbore and, when lowered into the well, seals against the wellbore wall and removes well fluids and solids that adhere to the inside of the wellbore. Typically, wipers have one or more cup-type elements that prevent flow. Examples of wipers are illustrated in U.S. Pat. Nos. 6,347,667 and 6,883,605 and U.S. Publication #2009/0126933. “Casing centralizer” refers to the device secured around a tubing string or tool, typically at regular intervals, to center it in the wellbore. A “gauge ring” is a ring assembled in a tubing string or tool used to measure, guide and centralize it in the wellbore.